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Dendritic cell function in allostimulation is modulated by C5aR signaling

Qi Peng1, Ke Li, Naiyin Wang

  • 1Complement Laboratory, MRC Centre for Transplantation, King's College London, School of Medicine at Guy's Hospital, London, UK.

Journal of Immunology (Baltimore, Md. : 1950)
|October 30, 2009
PubMed

Insights

Complement component 5a (C5a) directly activates dendritic cells (DCs) via C5aR, enhancing their T cell stimulation capacity. This involves modulating signaling pathways like PI3K/AKT and NF-kappaB.

Area of Science:

  • Immunology
  • Complement System
  • Cellular Signaling

Background:

  • The role of C5a in regulating T cell immunity is recognized, but its precise mechanisms and cellular targets remain unclear.
  • Dendritic cells (DCs) are crucial antigen-presenting cells that bridge innate and adaptive immunity, influencing T cell responses.

Purpose of the Study:

  • To investigate the direct effects of C5a-C5aR interaction on dendritic cell activation and their subsequent T cell stimulatory functions.
  • To elucidate the specific intracellular signaling pathways involved in C5a-mediated DC modulation.

Main Methods:

  • Utilized dendritic cells from C5a receptor knockout (C5aR-/-) mice and wild-type DCs treated with a C5aR antagonist.
  • Assessed DC activation markers (MHC class II, B7.2), cytokine production (IL-10, IL-12p70) following LPS stimulation.
  • Evaluated T cell stimulation capacity and analyzed intracellular signaling pathways (cAMP, PKA, PI3K/AKT, NF-kappaB).

Main Results:

  • DCs lacking C5aR or treated with antagonist showed reduced activation, decreased IL-12p70, increased IL-10, and impaired T cell stimulation.
  • Conversely, C5a stimulation enhanced DC activation, allostimulation capacity, and modulated signaling pathways.
  • C5aR stimulation inhibited cAMP production and PKA activity while activating PI3K/AKT and NF-kappaB signaling in DCs.

Conclusions:

  • C5a directly acts on C5aR expressed on DCs, promoting their activation and enhancing their ability to stimulate allospecific T cells.
  • The observed DC functional enhancement by C5a involves the down-regulation of the cAMP/PKA pathway and up-regulation of PI3K/AKT and NF-kappaB signaling.

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